This invention relates to a transfer device for transmitting a film card or a comparable object, guided between two guides from one position into another, for example, for transmitting a film card from a film platform into a film cassette.
In microfilm reading machines, it has been customary for a long time to move the film platform mechanically, so that a picture selected by means of a keyboard can be moved automatically in front of the objective. Further developed microfilm reading machines have also already appeared on the market, in which an automatic selective film card exchange between the film platform and a magazine is possible. In one such type of machine, the film cards are stored in a carousel. Each film card is provided with a clip exhibiting a coding in the form of notches, whereby selection is possible. Then, by a relatively complicated mechanism, the respective film card desired is withdrawn from the carousel and moved into the projection device, after the film card present there has previously been transported into the magazine.
In another type of machine, the film cards are kept in foil envelopes. They are stored, and slid into the film platform, in these foil envelopes. The foil envelopes have lugs, similar to index cards, by means of which selection is made. Experience has shown that such foil envelopes readily become scratched themselves and also scratch the film card. They also lead to a milky, blurred image in the microfilm reading machine and are the cause of Newtons rings.
Such problems could be avoided if, for example, a magazine constructed as a cassette was arranged vertically mobile and the respective film cards could simply be slid from the magazine in a straight line into the film platform and, conversely, a film card from the film platform slid in a straight line into the magazine. It would then be possible to omit a coding on the film cards and simple to move the magazine into that position in which the desired film card is aligned with the film platform.
A device of this type with film cards guided upright in slots is likewise known. However, the configuration of the transfer device is a problem with such a device. One generally thinks of a pair of rollers to transport the film cards, as in the case of copying machines, for example. However, since from considerations of space such a pair of rollers cannot grip between the stored film cards and extract a film card, a ram is additionally required which slides the respective film card out of the magazine into the induction region of the pair of rollers. A device must also be provided which slides the film card, after it leaves the pair of rollers, into a limit position on the film magazine, or into the magazine in the inverse transport direction. Because the film cards are frequently extremely thin, difficulties arise in sliding them reliably with rams. Moreover, the movement of the rams must be coordinated and monitored, which dictates substantial structural outlay.